This invention relates to a method of and an apparatus for welding sheet steel panels by the submerged arc technique.
Methods and apparatus of the contemplated kind are well known in the art. They avail themselves of one or more wire electrodes arranged in the weld gap in tandem and possibly bunched. The principal defect of such apparatus and welding machines is that they cannot carry very high currents, and that the possible welding speeds are limited accordingly. It follows that the parent metal is liable to be grossly overheated, and that the resultant weld seam tends to have unsatisfactory technological mechanical properties, particularly in the very highly heated zone adjacent the weld.
Welds are also made with the provision of additional filler metal carrying no current in the form of a plate (German Offenlegungsschrift No. 2,019,318), a wire (U.S. Pat. No. 3,816,694), and a wire grain (see Eichhorn, F., Shaheeb, A. F.: Einfluss technologischer und metallurgischer Massnahmen auf die Eigenschaften elektroschlackegeschweisster Verbindungen aus warmfester Stahlen. Z. F. Werkstofftechnik 4.Jg. 1973, No. 5, pages 229-236) or metal powder (see: Eichhorn, F., Hirsch, P.: Wesentliche Steigerung der Schweissgeschwindigkeit beim Elektro-Schlacke-Schweissen bei gleichzeigiger Qualitatsverbesserung der Verbindung. DVS-Bericht Band 31, 1974, pages 37-44; Ivochkin, I. I., Sosedov, A. F.: On the effectiveness of using filler metal in powder form in electroslag welding. Svar. Proiz. 1969, H. 11, pages 18-19; Smirnov, S. A., Efmienko, L. A. et al: Special structural features and mechanical properties of electroslag welded joints made using powdered filler metal. Avt. Svarka (1973), H. 9, pages 46-50), (German Auslegeschrift No. 1,026,898, German Auslegeschrift No. 1,040,148). In these processes the supplementary metal is introduced into the pool by gravity. However, as a matter of experience the introduction of the supplementary metal is liable to be interrupted by blockage in the feed tube caused by the powerful magnetic fields that arise in the weld gap, even when the welding currents are comparatively low. The welding speed is therefore still rather low, a circumstance which entails the above-mentioned drawbacks, the additional filler metal alone being unable to bring about an improvement in the structure of the weld.